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Although a cubic phase of Mn3Ga with an antiferromagnetic order has been theoretically predicted, it has not been experimentally verified in a bulk or film form. Here, we report the structural, magnetic, and electrical properties of antiferromagnetic cubic Mn3Ga (C-Mn3Ga) thin films, in comparison with ferrimagnetic tetragonal Mn3Ga (T-Mn3Ga). The structural analyses reveal that C-Mn3Ga is heteroepitaxially grown on MgO substrate with the Cu3Au-type cubic structure, which transforms to T-Mn3Ga as the RF sputtering power increases. The magnetic and magnetotransport data show the antiferromagnetic transition at TN = 400 K for C-Mn3Ga and the ferrimagnetic transition at TC = 820 K for T-Mn3Ga. Furthermore, we find that the antiferromagnetic C-Mn3Ga exhibits a higher electrical resistivity than the ferrimagnetic T-Mn3Ga, which can be understood by spin-dependent scattering mechanism.

A proximity effect between magnetic materials and topological surface states can generate and modulate the localized spins without complicated material structures, but its origin is not clearly verified. MnSi single layer and MnSi/Bi2Se3 bilayer on Al2O3(001) substrates are fabricated by magnetron co‐sputtering and molecular beam epitaxy systems, in which a large proximity effect between the chiral magnetic structure and the topological surface states is manifested. The magnetic and electronic properties of both samples are meticulously compared and the proximity‐induced magnetism enhancement in the MnSi/Bi2Se3 bilayer is found. Interestingly, this effect persists up to temperatures above 300 K. Furthermore, for the MnSi/Bi2Se3 bilayer, the increase of charge carrier density and the decrease of carrier mobility near the Curie temperature TC = 40 K are observed, which can mediate the ferromagnetic exchange interaction enhancing the magnetization. The finding provides insight into a new platform to consist of materials with distinct topological phases for future spintronic devices.

Topologically protected chiral skyrmions are an intriguing spin texture that has attracted much attention because of fundamental research and future spintronic applications. MnSi with a non-centrosymmetric structure is a well-known material hosting a skyrmion phase. To date, the preparation of MnSi crystals has been investigated by using special instruments with an ultrahigh vacuum chamber. Here, we introduce a facile way to grow MnSi films on a sapphire substrate using a relatively low vacuum environment of conventional magnetron sputtering. Although the as-grown MnSi films have a polycrystalline nature, a stable skyrmion phase in a broad range of temperatures and magnetic fields is observed via magnetotransport properties including phenomenological scaling analysis of the Hall resistivity contribution. Our findings provide not only a general way to prepare the materials possessing skyrmion phases but also insight into further research to stimulate more degrees of freedom in our inquisitiveness.

The key of spintronic devices using the spin-transfer torque phenomenon is the effective reduction of switching current density by lowering the damping constant and the saturation magnetization while retaining strong perpendicular magnetic anisotropy. To reduce the saturation magnetization, particular conditions such as specific substitutions or buffer layers are required. Herein, we demonstrate highly reduced saturation magnetization in tetragonal D022 Mn3–xGa thin films prepared by rf magnetron sputtering, where the epitaxial growth is examined on various substrates without any buffer layer. As the lattice mismatch between the sample and the substrate decreases from LaAlO3 and (LaAlO3)0.3(Sr2AlTaO6)0.7 to SrTiO3, the quality of Mn3–xGa films is improved together with the magnetic and electronic properties. Especially, the Mn3–xGa thin film epitaxially grown on the SrTiO3 substrate, fully oriented along the c axis perpendicular to the film plane, exhibits significantly reduced saturation magnetization as low as 0.06 μB, compared to previous results. By the structural and chemical analyses, we find that the predominant removal of Mn II atoms and the large population of Mn3+ ions affect the reduced saturation magnetization. Our findings provide insights into the magnetic properties of Mn3–xGa crystals, which promise great potential for spin-related device applications.